Cooling tower top forming method

ABSTRACT

A method for forming a top for a cooling tower having a bottom wall at least one opening therein for accommodating an air current generator. The cooling tower top additionally includes a plurality of hot liquid distributors for distributing hot liquid. The cooling tower top also includes a top wall having an opening for accommodating an air cooling generator and a liquid inlet.

PRIORITY

This application is a divisional application, and claims the benefit ofU.S. patent application Ser. No. 10/021,048, filed Dec. 19, 2001,entitled COOLING TOWER TOP METHOD AND APPARATUS, now U.S. Pat. No.6,736,374 B2, which claims the benefit of 60/330,896 filed Nov. 2, 2001the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a method and apparatus forthe disposal of heat utilizing a heat exchange liquid. Moreparticularly, the present invention relates to a method and apparatusfor a cross-flow water cooling tower wherein the water cooling tower isemployed, for example, to dispose of large quantities of heat generatedby various industrial processes.

BACKGROUND OF THE INVENTION

Cooling towers are used in many applications. For example, airconditioning systems for large buildings employ cooling towers forcarrying out a portion of the heat exchange that is essential to thecooling process. Industrial processes, such as chemical production,metals production, plastics production, food processing, etc., generateheat that must be disposed of, often by the use of cooling towers. Thecooling tower is a housing that channelizes air in proximity to a heatexchange liquid, for example, water. A heat exchange fluid may becirculated through the cooling tower and at least one fan may be mountedon the cooling tower to produce a flow of cooling air in proximity tothe heat exchange liquid. Heat is transferred from the heat exchangefluid to the air, largely through the evaporation of a small percentageof fluid which substantially lowers the temperature of the primary heatexchange fluid. The cooled heat exchange fluid can then return to theindustrial process to perform a heat exchange function for eitherindustrial processes or commercial air conditioning systems.

Conventional cross-flow cooling towers are presently in widespread usein such areas as factory complexes, chemical processing plants,hospitals, apartment and/or condominium complexes, warehouses andelectric generating stations. Conventional cross-flow cooling towers areconstructed with upright unitary or sectionalized fill structuressurmounted by hot water distribution basins and cold water collectionbasins. The hot water basins are usually equipped with target nozzles orother hot water distributors which distribute the incoming water overthe fill. The interior space bounded by the fill structures and the coldwater basins define the plenum for the tower. A fan assembly made up ofan apertured horizontal deck, which supports an upright, venturi-shapedstack, is positioned at the upper opening of the water cooling tower.This configuration provides a plenum large enough to enable a smoothtransition of the flow gas from the generally horizontal direction,through the fill assembly, to the generally vertical direction, and outthe exhaust port of the tower assembly. In the operation of thecross-flow cooling towers, hot water is introduced at the top of thefill while the air is introduced along the upright sides of the tower.As the water descends in an even distribution along the fill section,the cooling cross-flow air currents intersect the descending water in aheat exchanging relation. Subsequently, the cooled water is collected ina water basin below while the hot, moist air is discharged into theatmosphere.

In a cross-flow cooling tower, there is no necessity for the air to makeradical changes of direction into the fill and the air inlet is spacedalong the entire height of the fill. Therefore, the overall air pressurelosses in the fill are usually less than those of a conventionalcounter-flow tower resulting in the passing of air through the towermore easily.

Conventional cross-flow cooling towers generally employ variousvarieties of splash-type fill sections consisting of elongated bars of aspecific configuration for dispersing the descending released water.More recently, film type fill sections have been developed which haveproven substantially more efficient than splash fill sections. Thesetypically corrugated film fills generally consist of a series of thin,opposed sheets formed of synthetic resin materials in which water passesalong the sheets of “film”.

The highest potential for cooling exists at the top of the air inletsides where the hottest water comes into contact with the coldest air.Once such air has been heated such that the wet bulb temperature of theair is near the water temperature, the air has no more capacity to coolthe water, and such heat saturated air prevents the introduction ofcooler ambient air into the fill. Air near the top of the towertypically experiences this condition because it initially contacts thehottest water, and all other water along its path of travel is about thesame temperature. Air entering near the bottom of the tower initially isexposed to water that has been significantly cooled. As it traversesthrough the fill, the temperature of the water encountered by the bottomair currents rises, which allows the air to take on more heat.

The hot water basins in a cross-flow tower are normally constructed toserve as an air seal to prevent air entering the tower through the topof the fill. Additionally, air seals along the length of the tower areprovided along the inboard and outboard edges of the basins to seal fromthe bottom of the basins to the top of the fill. These seals prevent airfrom entering the spray chamber and bypassing the fill structure.Sealing of the distribution basins also minimizes the contact betweenincoming air currents and relatively large water particles adjacent thespray nozzles or water distributors.

Presently, a majority of unitary cooling towers are assembled from aplurality of pieces of sheet metal that are mounted to a metallicsupport frame. Unitary cooling towers typically are manufactured at alocation remote from the installation site. The towers are then shippedto the installation site in a substantially assembled form. Due to themetallic materials with which the cooling towers are assembled, thetowers are fairly heavy and therefore require extensive structuralsupport. In addition, the cost of present cooling towers are alsoadversely affected by the labor intensive processes for manufacturingand assembling the various metallic components of the cooling towers.

Metallic cooling towers are also subject to corrosion and/or rust. Thus,the metallic towers have a relatively short operational life. Corrosionand/or rust problems can be deterred by employing corrosion and/or rustresistant alloys. However, these metallic materials significantlyincrease the manufacturing cost of the water cooling tower.Alternatively, plastics such as polyethylene are well known for beingmoldable into prescribed form and function and are utilized in the art.However, polyethylene material properties are relatively weak andflexible. To compensate for these properties in monolithic parts,designers must use large quantities of polyethylene to create bigger,thicker and deeper sections to minimize stresses and deflections.

Accordingly, it is desirable to provide a cooling tower design thatoffers a substantial reduction in parts, avoiding complex and costlyassembly of components. It is also desirable to manufacture a watercooling tower that is light in weight, durable and resists corrosion.

SUMMARY OF THE INVENTION

The foregoing needs are met, to a great extent, by the present inventionwhere, in one aspect, a cross-flow cooling tower is provided having aframe assembly that is unitarily molded from a plastic material. Theframe assembly has opposed top and bottom walls that are parallel to oneanother along with opposed, parallel side walls that extend between thetop and bottom walls. The frame assembly also has opposed, parallel endsthat similarly extend between the top and bottom walls. The cross-flowcooling tower additionally has a vertical stack that extends verticallyfrom the top wall. The top covers of the cross-flow cooling towerproject outwardly and downwardly from the vertical stack, contacting theside walls and the opposing ends of the water cooling tower.

In accordance with another aspect of the present invention, a frameassembly is provided having a shell unitarily molded from plasticmaterial. The unitary shell includes opposed parallel top and bottomwalls along with opposed parallel end walls. The aforementioned sidewalls and ends both extend between the top and bottom walls.

In accordance with yet another aspect of the present invention, a topfor a cooling tower is provided having a hot liquid inlet and agenerally planar bottom with at least one opening therein foraccommodating an air current generator. In addition, the planar bottomhas a plurality of hot liquid distributors oriented to distribute hotliquid. The cooling tower top additionally has opposed parallel sidewalls unitarily connected to the bottom wall. In addition, the coolingtower top has opposed, parallel end walls connected to the bottom wall.The aforementioned side and end walls are unitarily connected to a topwall wherein the top wall has at least one opening formed therein foraccommodating an air current generator. The top wall projects outwardlyand downwardly from the opening.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described below andwhich will form the subject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein, as well as the abstract, are for the purpose ofdescription and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cross-flow cooling tower in accordancewith a first embodiment of the present invention.

FIG. 2 is a perspective view of a rotationally molded unitary frameassembly of the first embodiment of the present invention with towercovers unitarily attached to the opposing frame ends.

FIG. 3 is a top view of a top tower cover in accordance with the firstembodiment of the present invention after the cover has been detachedfrom an opposing end of the unitary frame assembly illustrated in FIG.2.

FIG. 4 is a perspective view of the rotationally molded unitary frameassembly of the first embodiment of the present invention with the towercovers removed from the frame ends revealing the air intake ports of theframe assembly.

FIG. 5 is a perspective view of a cross-flow cooling tower in accordancewith the first embodiment of the present invention with the rotationallymolded unitary frame assembly shown in phantom.

FIG. 6 is a side cross-sectional view of a cross-flow cooling toweraccording to the first embodiment employing a rotationally molded,unitary frame assembly with top covers.

FIG. 7 is a perspective view of a second embodiment of a cross-flowcooling tower in accordance with the present invention.

FIG. 8 is a perspective view of a hot water distribution unit inaccordance with the second embodiment of present invention.

FIG. 9 is a partial, cutaway view of the hot water distribution unit inaccordance with the second embodiment of the present invention andshowing a distribution pan or tray contained therein.

FIG. 10 is a perspective view of the underside of the hot waterdistribution unit of FIG. 9 in accordance with the second embodiment ofthe present invention.

FIG. 11 is a perspective view of an alternative two-piece hot waterdistribution unit in accordance with the second embodiment presentinvention.

FIG. 12 is a top view of a cold water collection basin in accordancewith the second embodiment of present invention.

FIG. 13 is a perspective view a flow splitter employed in a preferredembodiment of the present invention.

FIG. 14 is a perspective view of a flow splitter employed in a preferredembodiment of the present invention.

FIG. 15 is a perspective view of two liquid collection basins that aremolded together as one entity and then separated in accordance with analternative embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to the figures wherein like reference numerals indicatelike elements, FIGS. 1-15 illustrate the presently preferred embodimentsof a cross-flow cooling tower. While in the embodiment depicted thetower is a water cooling tower, it should be understood that the presentinvention is not limited in its application to water cooling towers, andcan be used for other types of cooling towers.

Referring now to the first embodiment illustrated in FIGS. 1-6, across-flow cooling tower, generally designated 10, is illustrated forcontacting generally horizontally flowing gas in a cooling relationshipwith generally vertically descending liquid. As seen in FIG. 4, thecooling tower includes a frame assembly 12 that is unitarily molded frompolyethylene in a rotational mold, illustrated in FIG. 2, having a top14, a bottom 16, two opposed side walls 18 and two opposed ends 20. Moreparticularly, as seen in FIGS. 1-6, the tower is made up of a unitarilymolded polyethylene frame assembly 12 reinforced by a mill galvanizedsteel skeleton 24, two upright fill assemblies 26, a hot waterdistributor 28 located above the fill assemblies 26, a vertical stack 30extending upwardly from the hot water distributor 28, a cold watercollection basin 32 below the fill assemblies 26, air intake ports 36,an exhaust port 39 and a cooling air current generator employing a fanunit 37. Skeleton 24 may be composed of other suitable materials such asstainless steel, hot dipped galvanized steel, epoxy coated steel, FRP(fiber reinforced plastic), etc. Fill assemblies 26 extend across theentire faces of air intake ports 36. Only a few fill sheets are shown inassemblies 26 to add clarity to the structural features of tower 10.

After removal of the covers 34, the unitary frame assembly 12 includestwo opposed side walls 18 that extend parallel to one another and areunitarily connected to a bottom generally planar wall and a top planarwall. The side walls 18 intersect the top generally planar wall to formthe sides of the hot water distributor 28 above the fill assemblies 26and intersect the bottom generally planar wall to form the side walls ofthe cold water collection basin 32 below the fill assemblies 26. As canbe observed in FIG. 2, the opposed ends 20 of the frame assembly 12intersect both the top and bottom generally planar walls of the coolingtower, forming the end barriers to the hot water distributor 28 and thecold water collection basin 32 respectively.

As illustrated in FIG. 2, initially, the unitarily polyethylene frame 12is rotationally molded having solid opposing ends 20 wherein the coolingtower covers 34 are molded to be included within the opposing ends 20.Upon completion of the molding process, the solid opposing ends 20 andthe tower covers 34 connected therein, are removed from the unitaryframe 12 by a cutting means. The tower covers 34 are then prepared forinstallation and assembly above the hot water distributor 28. As aresult of the removal of the tower covers 34, the opposing ends 20 ofthe cooling tower are designated air intake ports 36 when the tower isin operation. The aforementioned rotational molding of the unitary framebody 12 and following removal of the tower covers 34 offers a costeffective way for manufacturing and assembling a cross-flow watercooling tower by limiting the waste of manufacturing materials and bysubstantially reducing the amount of parts and assembly required.

In lieu of molding the tower covers 34 in opposed ends 20, louvers toprevent splash out of water may be molded into this face. Air inletopenings may be fabricated by removing the material around the intendedlouver structure. Molding the louvers in this face negates therequirement for attaching separate louvers or providing fill withintegral louvers.

As illustrated in FIG. 4, the unitarily molded frame assembly 12includes a hot water distributor 28 with a vertical stack 30 extendingvertically therefrom and a cold water collection basin 32 disposed belowthe distributor. The frame 12 additionally includes two opposing sidewalls 18 that extend parallel to one another between the collectionbasin 32 and hot water distributor 28. The assembly also has twoopposing intake ports 36.

The hot water distributor 28 contains a distribution pan or tray 38positioned directly above the fill assemblies that permits water togravitate through a plurality of apertures, perforations and/or nozzles41 onto the top surfaces of the upper film sections of the fillassemblies 26. The water is supplied to the distribution pan or tray byway of supply pipe (not shown) and enters the assembly via the waterinlet 40 shown in FIG. 1. Water is delivered to hot water distributor 28and is distributed evenly to both sides with the aid of a generallyinverted “V” shaped flow splitter 90 as illustrated in FIGS. 13 and 14.Flow control devices or valves are not required to balance the flow.Flow splitter 90 divides the flow and provides a barrier to preventtransitory or oscillatory flow variation from side to side.

The cold water collection basin 32 is disposed below the fill assemblies26 in a position to receive liquid gravitating therefrom. The basinextends across the entire width of the cooling tower 10 and may becoupled to a pumping structure (not shown) suitable for removingdeposited liquid therein and for delivering the water to equipmentrequiring the same for cooling and/or returning the water to the supplysource.

Referring now to FIG. 5, the polyethylene frame of the cooling tower 10and components contained therein, are supported by conventional millgalvanized steel framework 24 as shown. The framework 24 offers supportand strength to the tower frame while making the tower more durable,extending the cooling tower's operational life.

Polyethylene is a well-known plastic material used substantially forliquid containers such as milk jugs, and gallon gasoline containers.Polyethylene is a relatively inexpensive plastic and is dependable forcontaining liquids at low-pressure. However, polyethylene has relativelylow material mechanical properties. The modulus of elasticity is onlyabout 80,000 psi to 100,000 psi. By contrast the modulus of elasticityof steel is 29,000,000 psi which is about 300 times that ofpolyethylene. The implications for deflections are huge. For simplebeams of the same geometry and loading, the one made of polyethylenewill deflect 300 times the deflection of the steel beam. Therefore, tolimit the deflections of polyethylene structures, the unsupported spansmust be reduced very substantially and/or the cross-section increasedvery substantially compared to steel structures.

For example a simply supported beam subjected to a uniform loadexperiences a maximum deflection, Δ, according to following equation:

Δ=5 w L ⁴/(384 EI)  (1)

in which

w≡uniform load per unit length

L≡length of simple span

E≡modulus of elasticity

I≡moment of inertia of the beam cross-section

To maintain the same deflection for a given span, L, and given uniformload, w, the product of EI for each beam must be constant:

E_(p)I_(p)=E_(s)I_(s)  (2)

in which subscripts p and s are polyethylene and steel respectively.

Solving for the required polyethylene moment of inertia gives thefollowing equation:

I _(p) =I _(s) E _(s) /E _(p)  (3)

Taking the modulus of elasticity as 29,000,000 psi for steel and 100,000psi for polyethylene, the required polyethylene beam moment of inertiais $\begin{matrix}\begin{matrix}{I_{p} = {I_{s}\left( {29,000,{000/100},000} \right)}} \\{= {290\quad I_{s}}}\end{matrix} & (4)\end{matrix}$

For a simple rectangular beam cross-section the moment of inertia iscomputed as follows:

I=bh ³/12  (5)

in which

b=beam width

h=beam height

Assuming a constant proportion of the width, b, to the height, h, themoment of inertia can be rewritten as:

I=αh ⁴/12  (6)

in which

α≡b/h or b=αh

Substituting equation 6 with respective subscripts for steel andpolyethylene in equation 4 and solving for the height of thepolyethylene beam cross-section gives the following equation:$\begin{matrix}\begin{matrix}{h_{p} = \left( {290\quad h_{s}^{4}} \right)^{0.25}} \\{= {4.13\quad h_{s}}}\end{matrix} & (7)\end{matrix}$

Therefore, the cross-section of the polyethylene beam must be over 4times wider and over 4 times higher to carry the same load and maintainthe same deflection for a given span.

The cross-sectional area, A, for the rectangular cross-section is

A=b h  (8)

Substituting the proportionality constant expression, b=αh, fromequation 6 gives the equation

A=α h²  (9)

The cross-sectional area of the polyethylene beam, A_(p), is$\begin{matrix}\begin{matrix}{A_{p} = {\alpha \quad h_{p}^{2}}} \\{= {\alpha \quad \left( {4.13\quad h_{s}} \right)^{2}}} \\{= {17.1\quad \alpha \quad h_{s}^{2}}} \\{= {17.1\quad A_{s}}}\end{matrix} & (10)\end{matrix}$

Therefore, the cross-sectional area of the polyethylene beam is over 17times that of the steel beam. The specific gravity of steel andpolyethylene relative to water are about 7.85 and 0.94 respectively.Steel weighs about 7.85/0.94=8.4 times as much as polyethylene for thesame volume of material.

The volume of the beam, V, is

V=A L  (11)

The volume of the polyethylene beam may be expressed in terms of thevolume of the steel beam as follows: $\begin{matrix}\begin{matrix}{V_{p} = {A_{p}\quad L}} \\{= {17.1\quad A_{s}\quad L}} \\{= {17.1\quad V_{s}}}\end{matrix} & (12)\end{matrix}$

The weight of the beam is determined by multiplying the specific weight,γ, times the volume.

W_(s)=γ_(s) V_(s)  (13)

W_(p)=γ_(p) V_(p)  (14)

$\begin{matrix}\begin{matrix}{W_{p} = {\left( {\gamma_{p}/\gamma_{s}} \right)\quad \gamma_{s}\quad \left( {17.1\quad V_{s}} \right)}} \\{= {17.1\quad \left( {\gamma_{p}/\gamma_{s}} \right)\quad W_{s}}}\end{matrix} & (15)\end{matrix}$

The specific weight of steel, γ_(s), is 490 lb/cf, and the specificweight of polyethylene is about 59 lb/cf. Therefore, the weight of thepolyethylene beam compared to the weight of the steel beam may beexpressed as follows: $\begin{matrix}\begin{matrix}{W_{p} = {17.1\quad \left( {59/490} \right)\quad W_{s}}} \\{= {2.06\quad W_{s}}}\end{matrix} & (16)\end{matrix}$

Therefore, the polyethylene beam is actually more than twice the weightof the steel beam.

Furthermore, rotationally molded polyethylene costs more per unit weightthan does fabricated heavy mill galvanized (HMG) steel per unit weight.Thus, it is not economical to directly replace an HMG steel beam with apolyethylene beam as it would cost more than twice as much.

The yield strength of polyethylene ranges from about 1300 psi to 2800psi. The yield strength of steel is about 36,000 psi, which is about 28to 13 times the strength of polyethylene. However, polyethylene is aviscoelastic material which creeps (or moves) under sustained load. Longterm sustained stress levels must be kept low to prevent thisviscoelastic behavior from causing unacceptable deflections over time.Steel does not creep and is not subject to this limitation.

Taking the beam example above for constant deflections, the maximumbending stress, f_(b), may be computed from the following equation:

f _(b) =M/S  (17)

in which

M≡bending moment=w L ²/8  (18)

S≡section modulus=b h ²/6=αh ³/6  (19)

The section modulus of the polyethylene beam may be expressed in termsof the section modulus of the steel beam as follows: $\begin{matrix}{S_{p} = {\alpha \quad {h_{p}^{3}/6}}} \\{= {\alpha \quad {\left( {4.13\quad h_{s}} \right)^{3}/6}}} \\{= {70.4\quad \left( {\alpha \quad {h_{s}^{3}/6}} \right)}} \\{= {70.4\quad S_{s}}}\end{matrix}$

Therefore, since the bending moment is assumed constant for the example,the maximum bending stress in the polyethylene beam may be expressed interms of the maximum bending stress of the steel beam as follows:$\begin{matrix}{f_{bp} = {M/S_{p}}} \\{= {M/\left( {70.4\quad S_{s}} \right)}} \\{= {f_{s}/70.4}}\end{matrix}$

Steel members are often sized for a maximum stress of about 0.6 of theyield strength which is 0.6 (36,000 psi)=21,600 psi. The polyethylenemaximum bending stress would be 21,600 psi/70.4=307 psi. This is about0.1 to 0.2 times the yield strength of the polyethylene, which normallyis sufficient to control creep.

The structural comparisons above show that polyethylene is noteconomical for structural applications. On the other hand steel is verywell suited for structural applications and has been used in a widevariety of applications including unitary cooling towers. Polyethyleneis corrosion resistant and formable by rotational molding into multiplefunctional shapes. The two materials compliment one another in astructural hybrid cooling tower design to produce a cost effective,durable product. A steel skeleton provides load paths to support thepolyethylene components.

As illustrated in FIG. 6, the fill assemblies 26 of the tower employ upto a total of two film type fill packs or units which are aligned in aduplicate fashion in two opposed units so as to present a double-flowtower. Each of the units is made up of a plurality of upright, spacedapart film fill sheets of chevron or herringbone design. The film fillsheets are integrally constructed to include both louvers andeliminators, which for example, may be the type illustrated in U.S. Pat.No. 4,548,766. Each of the units and thus the overall fill assemblies26, present upright air inlet faces 42, opposed, upright air outletfaces 44, and a generally horizontal upper face 46 extending between theinlet face 42 and the outlet face 44. Therefore as a result of theindividual fill assembly orientation, the gas inlet 42 and outlet 44openings enable the flow of gas over substantially the entire verticalheight of the fill assembly into the central plenum chamber 48 of thewater cooling tower 10.

Alternatively, the air inlet 42 faces may be provided with stationarylouvers 50 utilized to prevent water from splashing out of the tower.Again, these louvers may be rotationally molded in opposed ends 20 inlieu of basin covers 34. A drift eliminator wall 52 can be disposedacross the air outlet faces 44 and in generally an upright position toprevent entrained droplets of water from entering the plenum chamber 48as spray. The wall may be of any type for example, a honey-comb typeeliminator or a series of spaced inclined baffles that permit the freeflow of air there through but prevent significant quantities of liquiddroplets from escaping the fill assemblies 26. An exemplary eliminatoris disclosed in U.S. Pat. No. 4,514,202. The fill assemblies 26, inconjunction with their respective eliminator walls, combine to form thetower's central plenum 48.

FIG. 6 illustrates that a vertical stack 30 is disposed above the hotwater basin 28 and extends upwardly from the central plenum chamber 48to define the exhaust port 39 of the cooling tower 10. The fan unit 37is positioned within the stack 30 and is supported by horizontal supportmembers 54 wherein the fan unit 37 employs a blade assembly coupled to amotor. Operation of the fan unit 37 causes currents of air to be drawnthrough the fill assemblies 26 and forces the currents upwardly throughthe plenum chamber 48 into the vertical stack 30 for discharge throughthe exhaust port 39.

A variety of alternative components and designs can be used in the watercooling towers of the present invention. FIG. 7 illustrates a secondembodiment of the present invention wherein a cooling tower 56 isdisplayed having a steel frame assembly composed of mill galvanizedsteel, and having a top, a bottom, two opposed side walls, two opposedends. More particularly, the tower consists of two opposed millgalvanized cold-formed steel side walls 58 parallel to one another, twoupright fill assemblies 60, a self contained hot water distribution unit62 above the fill assemblies 60, a cold water collection basin 64 belowthe fill assemblies 60, air intake ports 63, an exhaust port 65 and acooling air current generator employing a fan unit 66.

Referring now to FIGS. 7-11, and in accordance with the presentinvention, the hot water distribution unit 62 is rotationally moldedfrom polyethylene in one operation to produce a single, self enclosedunit that includes a generally planar, distribution pan or tray 68having apertures, perforations and/or nozzles 69, four walls 70unitarily connected to tower covers 72, and an opening 74 for towerexhaust. The covers 72 project outwardly and downwardly from the opening74. More particularly, the distribution unit 62 is a self contained unithaving a water inlet 76, a first set of opposing side walls 70 parallelto one another and second set of opposing sides walls 70 parallel to oneanother. Both sets of walls 70 extend vertically from the pan or tray 68and intersect the tower covers 72 to form a unitary enclosure, employedfor the distribution of hot water having a fan shroud 78. Raisedportions 73 are designed to manage water delivered to distribution unit62. Most importantly raised portions 73 serve to transform the inletpiping flow discharge disturbances into a more quiescent channel flowwhich is then released into distribution pans or trays 68. Anothersignificant benefit of raised portions 73 is reduction in the amount ofwater inventory carried in distribution unit 62, which reduces theoperating weight. The distribution unit 62 may be attached to thegalvanized steel frame of the water cooling tower 56 by fastening meanssuch as screw, welding, bolt, solder, and/or bracket.

In addition, as illustrated in FIG. 11, should the tower be sufficientlylarge such that a single piece distribution unit 62 would be impracticalto rotationally mold, the distribution unit 62 may be rotationallymolded as two or more individual pieces 67 that are subsequently joinedtogether to form a distribution unit 62.

Referring now to FIG. 12, the cold water collection basin 64 is disposedbelow the fill assemblies 60 in a position to receive liquid gravitatingtherefrom. The cold water basin 64 is a rotationally molded, unitarypiece having a generally planar bottom surfaces 80 and 81, a first setof opposed side walls 82 extending parallel to one another away from thebottom surfaces 80, 81 and a second set of opposed side walls 84extending parallel to one another away from the bottom surfaces 80, 81.The basin 64 extends across the entire width of the cooling tower andmay be coupled to a pumping structure suitable for removing depositedliquid therein and for delivering the water to equipment requiring thesame for cooling and/or returning the water to the supply source. Thecold water basin 64 may be attached to the galvanized steel frame of thewater cooling tower by fastening means such as screw, welding, bolt,solder, and/or bracket.

In addition, should the tower be sufficiently large such that a singlepiece collection basin 64 would be impractical to rotationally mold, thecold water collection basin 64 may rotationally molded as two or morepieces that are subsequently joined together to form a collection basin64.

In accordance with an alternative embodiment of the present invention,the hot water distribution unit 62 and collection basin 64 illustratedin FIGS. 7-11 may be rotationally molded together as one entity and thenseparated as illustrated in FIG. 15. As illustrated in FIG. 15, twobasins 92 and 94 respectively, are rotationally molded simultaneously ina single molding process. The basins 92 and 94 are then separated by acutting element. The basins are then incorporated into a water coolingtower assembly as previously described, wherein basin 92 is employed asa hot water distribution element and basin 94 is employed as a coldwater collection basin.

The aforementioned molding process is advantageous because it allows forthe creation of an enclosed mold which reduces the amount of wasteproduced during the molding process. If the basins were to be moldedseparately, a temporary top would be required to be molded for eachpiece so that the basin mold could be closed. The molded, temporary topportion would then have to be cut away from the basin to open it upresulting in wasted material. This embodiment does not include basincovers, however the covers may be fabricated separately and added to thetower assembly.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirits and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

What is claimed is:
 1. A method for forming a cooling tower top from aplastic material, said method comprising the steps of: molding agenerally planar bottom wall portion having at least one opening thereinfor accommodating an air current generator and having a plurality ofspaced apart hot liquid distributors oriented to distribute hot liquid;molding a top wall portion having at least one opening formed thereinfor accommodating an air current generator; and molding a liquid inletportion; wherein the aforementioned molding steps form a unitarilymolded, enclosed liquid distribution unit.
 2. The method of claim 1,wherein all three molding steps are carried out in a simultaneousmolding process.
 3. The method of claim 1, wherein the cooling tower topis rotationally molded.
 4. The method of claim 1, further comprising thestep of molding opposed, end walls that are unitarily connected to thebottom wall and the end walls extend vertically from the bottom wall. 5.The method of claim 1, further comprising the step of molding opposedside walls that are unitarily connected to the bottom wall and the sidewalls extend vertically from the bottom wall.
 6. The method of claim 5,wherein all four molding steps are carried out in a simultaneous moldingprocess.